Insulating support for ignition conductors



Aug. 22, 1961 J. OLDHAM ET AL INSULATING SUPPORT FOR IGNITION CONDUCTORS3 Sheets-Sheet 1 Filed Dec. 8, 1958 INVENTURS JOLDHAM RLSMITH F/GZ Aug,22, 1961 J, OLDHAM ET A 2,997,531

INSULATING SUPPORT FOR IGNITION CONDUCTORS Filed Dec. 8, 1958 3Sheets-Sheet 2 F/G.6 J.OLDHAM R. L .SM/ TH INVENTORS ATTORNEY-5 Aug. 22,1961 J. OLDHAM ET AL 2,997,531

INSULATING SUPPORT FOR IGNITION CONDUCTORS Filed Dec. 8, 1958 3Sheets-Sheet 3 J.OLDHAM /?.L.SM/TH JNVENTORS ATTORNEY United StatesPatent 2,997,531 HYSULATING SUPPORT FOR IGNITION CONDUCTORS JamesOldham, Allen Park, and Robert L. Smith, Grosse Ile, Mich., assignors toFord Motor Company, Dearbom, Mich., a corporation of Delaware Filed Dec.8, 1958, Ser. No. 778,769 '3 Claims. (Cl. 174-158) This inventionrelates to an ignition system of an internal combustion engine and moreparticularly to means in an ignition system of an internal combustionengine for reducing the capacitance between electrical conductorscarrying oscillating high voltage low power electrical energy and theinternal combustion engine.

In ignition systems for internal combustion engines, the electricalconductor which connects the secondary winding of the ignition coil withthe distributor and the electrical conductors which connect thedistributor with the spark plugs carry oscillating high voltage lowpower electrical energy. The oscillating wave form carried by theseelectrical conductors can readily be analyzed by standard electricalengineering techniques to determine that the oscillating wave formcontains high frequency components which may find a low capacitivereactance path to the ground reference point of the internal combustionengine, if the capacitance between the electrical conductors and theinternal combustion engine is high. These high frequency components maythus be eliminated from the voltage present at the spark gap of thespark plug thereby lowering the peak voltage present and resulting infailure to fire the fuel mixture in the combustion chambers,particularly during high speed operation and cold weather startingconditions.

The present invention has been developed to obviate these difiicultiesand to provide a convenient means of mounting the electrical conductors,which connect the distributor with the spark plugs, in spacedrelationship with respect to the engine components. According to theconstruction of the present invention, a clip member constructed ofinsulating material is provided and it comprises a main body portionhaving a plurality of fingers extending therefrom to receive and holdthe elec trical conductors. A metal plate is afifixed t0 the internalcombustion engine at some convenient point between the distributor andthe spark plugs, for example, on the top of the rocker arm cover. Theclip member is provided with legs which engage either side of the metalplate so that the clip member may be placed over said metal plate afterthe electrical conductors are posi tioned in engagement with the fingersof the clip member. Cooperating means are also provided on the metalplate and the clip member for frictionally retaining these two membersin engagement. The main body portion of the clip member is thuspositioned between the electrical conductors and the metal plate andsince this main body portion is constructed of insulating material andis of substantial thickness, the capacitance between the electricalconductors and the internal combustion engine is reduced. By theselection of the proper materials and dimensions the capacitivereactance between the electrical conductors and the internal combustionengine may be made sufiiciently great so that the drain of the highfrequency components of the oscillating electrical energy carried bythese conductors in negligible.

An object of the present invention is the provision of an ignitionsystem for an internal combustion engine in which the capacitancebetween electrical conductors in said system and the engine componentsis reduced to a minimum.

Another object of the invention is to provide a means for mountingelectrical conductors of an ignition system for an internal combustionengine such as that the capacitive reactance between the electricalconductors and the engine components is made sufficiently great so thatthe drain of high frequency components from the oscillating electricalenergy carried by said electrical conductors is substantiallynegligible.

A further object of the invention is the provision of a means formounting electrical conductors of an ignition system on an internalcombustion engine which is simple and readily assembled.

Other objects and attendant davantages of the present invention willbecome more readily apparent as the specification is considered inconnection with the annexed drawings in which:

FIGURE 1 is an elevational view of an internal combustion engineemploying the present invention;

FIGURE 2 is a circuit diagram of the ignition system employed with theinternal combustion engine shown in FIGURE 1;

FIGURE 3 is a partial circuit diagram of the ignition system shown inFIGURE 2;

FIGURE 4- is a perspective view of the clip member and metal plate ofthe present invention;

FIGURE 5 is an end view of the clip member shown in FIGURE 4;

FIGURE 6 is an elevational view of a separator of the present invention;

FIGURE 7 is a plan view of a sub-assembly of ignition wires, clip memberand separator ready for installation on an internal combustion engine;

FIGURE 8 is a View taken along the lines 88 of FIGURE 7.

Referring now to the drawings in which like reference numerals designatelike parts throughout the several views thereof there is shown inFIGURES 1 and 2 an ignition coil 11 having a primary coil 12 and asecondary coil 13. The primary coil is energized by a battery 14 througha switch 15 and is grounded though a ballast coil 16 and the breakerpoints 17 when the points are closed. When the breaker points 17 areclosed current flows from the battery, one terminal of which isgrounded, through the primary coil 12, through the ballast coil 16, andthen to ground through the breaker points. When the cam 18 opens thebreaker points 17, the magnetic field in the primary coil collapses veryrapidly with a substantial amount of the energy being absorbed by thecapacitor 21. The rapid collapse of the magnetic field in the primaryinduces a high voltage electromotive force in the secondary coil 13. Asthis action is repeated, that is, as the breaker points open and closedue to the action of cam 18, oscillating high voltage low powerelectrical energy is induced in the secondary winding 13 and is conveyedto rotor 22 of the distributor 23 by means of a conductor 24. Thiselectrical energy is then distributed to the spark plugs 25, 26, 27, 28,31, 32, 33 and 34 of the internal combustion engine by means ofinsulated conductors 35, 36, 37, 38, 41, 42, 43 and 44 which areconnected to the spark plugs and terminals of the distributor cap. Theoscillating electrical energy must possess sufficient peak voltage ateach spark plug to are across the spark plug gap, one electrode of whichis grounded, and thus complete the circuit to the secondary coil throughthe ground wire 40 of the secondary coil under all operating conditionsof the internal combustion engine and must also possess sufiicientelectrical energy to ignite the charge present in the cylinders underall operating conditions of the engine.

All of these components are mounted on an internal combustion enginesuch as a standard production type V8 engine 45 shown in FIGURE 1. It isevident that the insulated conductors leading from the distributor 23 tothe spark plugs must pass directly over a portion of the internalcombustion engine and unless supported in some way would be in directcontact With a portion of the engine, and in the particular engineillustrated, the rocker arm cover. With. the electrical conductorssupported upon the rocker arm cover either directly or by means of ametallic support structure affixed thereto, the capacitance between theinsulated conductors and the engine which is the ground reference pointof the electrical system is relatively high and the capacitive reactancetherebetween is relatively low thereby causing a loss of high frequencycomponents from the voltage present at the spark plug gap. This can bemore readily understood by reference to FlGURE 3 in which thecapacitance between one of the insulated electrical conductors leadingfrom the distributor to the spark plugs and the internal combustionengine is shown in dotted lines.

A study of FIGURE 3 will show that the capacitance between the insulatedelectrical conductors, for example conductor 35, which connect thedistributor 23 with the spark plugs, and the internal combustion engineis in parallel with the resistance and the spark gap of the spark plugs.If the capacitance reactance of this path is low, the high frequencycomponents of the electrical energy emanating from the secondary coil 13will tend to follow this path to ground-the internal combustionengineand will thus be eliminated from the voltage present at the sparkgap of the spark plugs, for example spark plug 25. Thus to have maximumvoltage present at the spark gap it is necessary to provide a highcapacitive reactance between the insulated conductor and the internalcombustion engine. The capacitive reactance of this path is determinedby the formula:

't can be determined from this formula that at a given frequency thecapacitive reactance varies inversely as the capacitance and thus toincrease the capacitive reactance of this path it is necessary to reducethe capacitance. It is well known that the capacitance between twoconductive members varies inversely as the distance between them. Byincreasing the distance between the conductors which connect thedistributor with the spark plugs and the engine, the capacitance can belowered and the capacitive reactance can be increased.

The present invention accomplishes a decrease in the capacitance betweenthe insulated electrical conductors designated by the numerals 3d thru33 and the numerals 41 thru 44 and the internal combustion engine bymounting these conductors in a clip member 51 which is constructed of aninsulating material having a dielectric constant approximately equal tothe dielectric constant of the insulation covering these conductors.This clip is mounted on a plate member 52 which has a first portion 53lying against and affixed to the rocker arm cover of the engine and asecond portion 54 which receives the clip member 51 and extends atapproximately a right angle to the first portion 53. A separator 55 ispositioned between the clip member 51 and the distributor 23 to alignthe electrical conductors so that they may be properly positioned in theclip member.

Referring now to FIGURES 4 and 5, there is shown the clip member 51 andthe plate member 52 in detail. The clip member 51 is constructed of aninsulating material having a dielectric constant approximately equal tothe dielectric constant of the insulation of the conductors carriedthereby, for example nylon, and includes a main body portion 56. Themain body portion has a plurality of arcuate fingers designated by thenumerals 57 thru 64 and these fingers together with the main bodyportion form a plurality of generally circular shaped slots 65 thru 68which are open along one side thereof to receive the electricalconductors on one side of the engine, for example conductors 35 thru 38.As can best be seen by reference to FIGURE 8, the width of theseopenings is slightly smaller than the diameter of the insulatedelectrical conductors so that the insulated conductors may be pressedinto the slots through the opening and securely held therein by thearcuate shaped fingers. The main body portion 56 of the clip member alsohas a first angularly shaped leg 71 and second angularly shaped leg 72extending therefrom. Each of these legs has a first surface 73 and asecond surface 74 which are disposed at right angles to one another. Thefirst surface 73 of the legs 71 and 72 he in the same plane, while thesurfaces 74 lie in spaced parallel planes which are substantially atright angles to the plane containing the surfaces 73 and are spaced fromone another a distance approximately equal to or slightly greater thanthe width of the second portion 54 of the metal plate 52. A third leg 75extends from the main body portion 56 and has a surface 76 which lies ina plane parallel to the plane containing the first surface 73 of thefirst and second legs 71 and 72 and spaced therefrom a distanceapproximately equal to the thickness of the portion 54 of metal plate52. This can best be seen by reference to FlGURE 5. The first surface 73of each of the legs 71 and 72 has a small integral protuberance 77 whichis adapted to be received in the apertures 78 in the second portion ofthe metal plate 52.

Referring now to FIGURE 6, there is shown an elevational view of theseparator 55. This separator has a main body portion 81 with arcuatefingers 82 through 85 extending therefrom to form with the main bodyportion a plurality of circular shaped slots 91 thru 94 which haveopenings along one edge thereof to receive the insulated conductors, forexample conductors 35 thru 38.

In the assembly of this invention the first portion 53 of the metalplate 52 is spot welded or otherwise suitably aflixed to the rocker armof the internal combustion engine. As can best be seen by reference toFIGURE 7, the insulated electrical conductors 35, 36, 37 and 38 whichhave affixed to one end thereof terminals 101 thru 104 and have afiixedto the other end thereof terminals 105 thru 198 are positioned withinthe circular shaped slots 65 thru 68 of the clip member 51. As can bestbe seen by FIGURE 8, this can readily be accomplished by forcing theinsulated conductor through the opening in these circular slots. Theconductors are similarly positioned in the circular shaped slots 91 thru93 of the separator member 55. The terminals 151 thru 104 are thensnapped into the proper position in the distributor 23 and the clipmember 51 is positioned over the second portion 54 of the plate member52. When so positioned, the second portion 54 extends into the spacebetween the first surfaces 73 of the first and second legs 71 and 72 andthe surface 76 of the third leg 75 and the protuberances 77 on thesurfaces 73 are received in the apertures 78 so that the clip member isfrictionally engaged and retained on the second portion 54 of the platemember 52. The terminals 105 thru 108 are then positioned in engagementwith the spark plug members 25 thru 28 and the assembly is complete forhalf of the engine. Of course, the same procedure and the same apparatusare em? ployed with the other half of the engine.

When the assembly operation is complete the clip member 5 1 and platemember 52 position the insulated electrical conductors in spacedrelationship with respect to the rocker arm cover so that thedistributed capacitance between the electrical conductors and the rockerarm cover is an inverse function of the distance therebetween. Also,there is interposed between the electrical conductors and the edge ofthe second portion 54 of the metal plate 52 the insulating material ofthe main body portion 56 of the clip member 511 and the capacitancetherebetween is an inverse function of the thickness of this main bodyportion. This effectively lowers the capacitance between the insulatedconductors connecting the distributor with the spark plugs and theinternal combustion engine over existing structures of this type.

It is thus apparent that the applicant has provided a means for loweringthe capacitance between the ignition conductors leading from thedistributor to the spark plugs and the internal combustion engine andthus lowering the loss of high frequency components of the high voltagelow power electrical energy carried by these conductors. This isaccomplished by the clip member and cooperating structure which alsogreatly facilitates the positioning of the electrical conductorsconnecting the distributor to the spark plug during assembly operations.It is also very convenient when repairs are necessary as the clip member5 1 may be readily disengaged from the plate member 52! by a sharp pullin an upward direction.

It will be understood that the invention is not to be limited to theexact construction shown and described, but that various changes andmodifications may be made without departing from the spirit and scope ofthe invention, as defined in the appended claims.

What is claimed is:

l. A support structure for ignition conductors of an internal combustionengine comprising a plate adapted to be affixed to the internalcombustion engine, a clip member constructed of an insulating material,said clip member comprising a main body portion having a plurality ofarcuate fingers extending therefrom and defining with said main bodyportion a plurality of generally circularly shaped slots being openalong a portion thereof, a plurality of legs extending from one edge ofsaid main body portion and having surfaces lying in one plane, anotherleg extending from said edge of said main body portion and having asurface lying in a plane parallel to the plane containing the surfacesof said first mentioned legs and spaced therefrom a distancesubstantially equal to the thickness of said plate so that said clipmember may be positioned upon said plate, with the plate beingpositioned between said legs and engaging the surfaces of said legs andso that the main body portion is positioned between said plate and saidignition conductors, and cooperating means on said clip member and saidplate for frictionally retaining said plate between the legs of saidclip member.

2. A support structure for ignition conductors of an internal combustionengine comprising, a plate adapted to be aifixed to the internalcombustion engine, a clip member constructed of an insulating material,said clip member comprising a main body portion having a plurality ofarcuate fingers extending therefrom and defining with said main bodyportion a plurality of generally circularly shaped slots open along aportion thereof, a first and a second angularly shaped leg extendingfrom said main body portion, each of said legs having a first surfaceand a second surface disposed at right angles to each other, the firstsurface of each of said legs lying in one plane, and the second surfaceof one of said legs lying in a plane parallel to a plane containing thesecond surface of the other of said legs, said last mentioned two planesbeing spaced at a distance substantially equal to the width of saidplate, a third leg extending from said main body portion and having asurface disposed in a plane parallel to the plane containing the firstsurface of said other two legs and being spaced therefrom a distancesubstantially equal to the thickness of said plate, a protuberancepositioned on the first surface of each of said first and second legs, apair of apertures positioned in said plate to receive saidprotuberances, said clip member being positioned over said plate suchthat the first surface of said first and second legs and said surface ofsaid third leg engage said plate on opposite sides thereof and saidprotuberances on the first surface of said first and second legs arereceived in the apertures in said plate and such that the second surfaceof said first and second legs overlie opposite edges of said plate.

3. A support structure for ignition conductors of an internal combustionengine comprising, a plate adapted to be affixed to the internalcombustion engine, a clip member constructed of an insulating material,said clip member comprising a main body portion having means forreceiving and retaining the ignition conductors, a plurality of legsextending from one edge of said main body portion and having surfaceslying in one plane, another leg extending from said edge of said mainbody portion and having a surface lying in a plane parallel to the planecontaining the surfaces of said first mentioned legs and spacedtherefrom a distance substantially equal to the thickness of said plateso that said clip member may be positioned upon said plate, with theplate being positioned between said legs and engaging the surfaces ofsaid legs and so that the main body portion is positioned between saidplate and said ignition conductors, and cooperating means on said clipmember and said plate for frictionally retaining said plate between thelegs of said clip member.

References Cited in the file of this patent UNITED STATES PATENTS1,403,827 Armathes Ian. 17, 1922 FOREIGN PATENTS 659,728 Great BritainOct. 24, 1951 796,532 Great Britain June 11, 1958

